The cylinder covers/cylinder head forms the top part of the combustion space and it must be of suffucient strength to withstand the gas load at maximum pressure.
The primary function of the cylinder cover is to close the end of the cylinder and to seal the gases involving extreme pressure and temperatures.The cover is exposed to high mechanical and thermal stresses.
Material used:- pearlitic or Nodular Graphite Cast Iron/Cast iron.
The cover lands on the top of the cylinder liner flange and is secured to the cylinder block by a number of cover studs and nuts.These are tightened hydraulically.
The covers also support various mountings and all the valve required to maitain the engine
In a two stroke large engine ,there may be large central exhaust valve,and cage ,2 or 3 fuek injectir,a starting valve,rekief valve &an indicator cock.
Medium speed 4 stroke diesel engines have two exgaust valve and two air inlet valve per cylindee,one centrally olaced fuel injector,an air starting valve,rekief valve,and indicator cock.
1.it should transfer heat readily
3.be symmetrical in shape
4.have coefficient of thermal expansion
Similar to liner.
They are circulated with fresh water from the jacket cooling system which maintains moderate temperatures and allows intensive cooling of the exhaust valve seating while making seoerate fuel valve cooling unnecessary.
Bore cooling arrangement are provided in modern cylinder covers,generally made up of cast steel.